Create Postgres database from pmm-managed

We need to create pmm-managed database from pmm-managed and we'll able to get rid from Ansible playbook from pmm-server + we'll able to initialize `/srv` dir

How to test:

1. Remove pmm-database and user:

supervisorctl stop pmm-managed
DROP DATABASE "pmm-managed";
DROP ROLE "pmm-managed";

2. start pmm-managed:

supervisorctl start pmm-managed

Database and role should be recreate